Ninja: 1,000 Years of the Shadow WarriorsBy John Man (Bantam Press 293pp £20)

A nineteenth-century print of the attmepted assassination of Nobunaga in 1573

John Man studied Mongolian languages at SOAS and become an expert on ancient Mongol military history and the surging hordes of Genghis and Attila. He hotfooted it to Ulan Bator and the endless grasslands of the Mongolian steppe for field research, an enterprise that proved so successful that Man was awarded a Mongolian gong for advancing British-Mongolian relations. He is also an expert in philology, but not, so far as I can discover, able to speak or read Japanese.

Despite this language handicap, perhaps significant for a popular historian accustomed to going deep into primary sources, in 2011 Man wrote an account of the Satsuma uprisings of Saigo Takamori, a remarkable man who was the inspiration for the Tom Cruise movie The Last Samurai. When this Hollywood epic first came out I asked the aikido master Chida Tsutomu what he thought of it. He paused, cleared his throat and, smiling, said: 'It made me want to visit New Zealand.' Western encounters with Japan so often prefer myth to truth, fiction to fact.

Three Mongolian books under the belt, one on Japan published, so why not another on Japan and then perhaps another? The topic of this second book, however, is as elusive as the ninja themselves. More correctly called shinobi (although every region of Japan and period of history has used different terms), ninja were a group of independent, special forces-like combatants for hire, comprising both samurai and non-samurai, who focused on covert operations: what in modern military jargon would be called 'black ops', the often deniable operations that, if entirely successful, would appear to be the work of someone else or not to have happened at all. Except that someone would be dead, hostages would have been rescued, or a castle would have been destroyed or captured.

Man sets out the various theories about the origins of ninja skills: they may have come from China, or from mountain ascetics called yamabushi, or from dissident warrior monks, or from pirates or bandits. Ninja lore was probably crafted and consolidated from all these sources. Shinobi were also geographically specific and focused on the close-knit and intermarried communities of Kouka and Iga in central Honshu, not far from Nara. The location was defensible and the self-governing communities farmed and sold their covert skills to anyone who could pay, sometimes fighting on both sides of a conflict.

Ninja methods, or shinobi no jutsu, were not martial arts. They were instead a range of strategies for infiltration, disguise, concealment and espionage, which also included expertise in arson and harassing the enemy. In every sense the range of tasks performed by ninja are those today assigned to special forces. Only the command structure differed: ninja were freelance.

As part of his ruthless consolidation of power, the sixteenth-century warlord (and the first ruler to unify Japan) Oda Nobunaga eventually moved against the mountainous ninja territories, attacking them in force in 1587. Any documents recording techniques and strategies, which had been carefully concealed in farms and temples, went up in smoke; for the survivors of this attempted ninjacide, a ninja diaspora was created. Decades later, in the less anarchic times of a Tokugawa-imposed peace, and with ninja now employed by local lords, manuals of ninja doctrines were written down, including the Ninpiden (perhaps dating from 1560, but transcribed in 1731), the Bansenshukai (1676) and the Shoninki (1681).

Unpacking ninja history requires careful examination of the myths and crazes that have gripped the popular imagination. Several waves of ninja mania have washed over the West. Naturally enough these started in Japan in the late 1950s with novels and manga comics. In the 1960s the movie Shinobi no mono, directed by Yamamoto Satsuo, rekindled the craze and, like a pandemic, it spread next to the US in the 1970s and migrated to the UK in the 1980s. There were urgent public pleas to ban nunchaku - an Okinawan weapon never used by ninja but much loved by Bruce Lee - and shiho-shuriken (or throwing stars). Finally the mania crossed the species barrier with Teenage Mutant Ninja Turtles in 1987.

But what did anyone actually know of ninja? They were mostly men, sometimes masked, hiding in shadows, able to move undetected and to use a host of martial skills to achieve their impossible missions. Unlike the death-obsessed samurai, they were pragmatic. They were often sent to spy out an enemy stronghold and to do this effectively they needed to return successfully to base. Assassins of infinite patience, they were light (the ideal ninja was a flyweight 132 lb), flexible and able to hide by hooking on to ceilings. They could silence dogs, and disguised their body odour with a bland tofu diet. One famous ninja was a dwarf who, according to some accounts, assassinated a heavily guarded warlord, Uesugi Kenshin (who may actually have been a woman in drag), by hiding in his castle toilet and drilling him per anum with a telescopic spear. Man reasonably speculates on this story and wonders how a shit-coated dwarf ninja managed to sneak out of a castle on high alert.

The least convincing part of the book is an attempt to bridge the centuries and show how an extinct set of skills was maintained in the Nakano spy school, established in 1938 to train infiltration agents. We learn of the bizarre endurance of one of its graduates, Onoda Hiroo, who spent thirty years after the Second World War had ended hiding in the Philippine jungles before finally being tempted out and repatriated to a hero's homecoming. Ninja is a racy popular history of a difficult and often mythologised subject and should appeal to the armchair warrior in us all.

Christopher Ross lived in Japan for five years, has a black belt, though not in ninjutsu, and is the author of Mishima's Sword.

Retraction: it has been brought to our attention that certain details of John Man's career originally featured in this review were incorrectly attributed to him. These elements have now been removed, and Literary Review apologises for any confusion caused by this misattribution.